The present invention relates to a facsimile transceiver, printer, copier or similar image forming apparatus and, more particularly, to a multiplex image forming apparatus which is the combination of such apparatuses.
An image forming apparatus of the type described generally includes means for preventing dew condensation from occurring thereinside. Such anti-dew condensation means is especially indispensible in environments which cause the room temperature to sharply change, e.g., in cold districts. The anti-dew condensation means is usually implemented as a heater incorporated in an AC power source line. It is a common practice to use, for example, a cord heater or a cement resistor as the anti-dew condensation means. Specifically, when a power switch is turned off, an opposite contact associated with the power switch is closed to energize the heater. The heater is arbitrarily located in the vicinity of a lens, mirror or similar part whose thermal conductivity is low or a metallic member having a substantial mass, e.g., the shaft of a photoconductive element or that of a roller. Since an AC power source in the form of a primary circuit is incorporated in the apparatus, such a heater makes it difficult to isolate the primary circuit from a secondary circuit for eliminating noise terminal voltage and radiation noise. Moreover, the conventional heater is susceptible to noise generated on the AC power source line and extraneous noise ascribable to, for example, a thunderbolt, resulting in complicated countermeasures.
A multiplex image forming apparatus having multiple functions, e.g., facsimile function, printer function and copier function is a recent achievement. A Japanese Patent Laid-Open Publication (Kokai) No. 57870/1989, for example, discloses a multiplex image forming apparatus which is the combination of a facsimile transceiver and a copier. In such an apparatus, even when a power source for the copier is turned off, it is automatically turned on when the facsimile transceiver receives data from a remote station. Then, the copier prints out the received data. This type of apparatus is provided with a main power source and a scanner power source. The main power source includes a detector responsive to the AC power source line. When the facsimile transceiver operates in a receive mode at night, a fixing heater and other constituents of the apparatus to be not used are deactivated to save power while preserving the facsimile function. However, since a control circuit incorporated in the apparatus is active at all times, a noticeable power saving effect cannot be expected. Further, with this conventional apparatus, it is impossible to reduce the power consumption by the DC power source during reception at night. In addition, in the receive mode operation at night, a cooling fan has to be rotated to cope with heat generation ascribable to power consumption, resulting in the increase in noise.